1. Field of the Invention
This invention relates to apparatus which respond to a predetermined acceleration. More particularly it relates to devices for detecting if a shock or force or acceleration has occurred which could harm the item to which the device is associated or attached.
2. Description of the Prior Art
The prior art has seen the development of a wide variety of complex electronic, mechanical, and magnetic apparatus delicate enough that shocks, as small as those received during transportation, can cause the apparatus to malfunction or fail. Often these failures are not easily noticed by examination of the apparatus itself and a separate shock detection device is, therefore, desired. An example of a delicate apparatus of the type described is a magnetic disc package used to store large amounts of information for access by computers. If these discs receive a large enough shock then a magnetic disruption of the information contained on the disc can occur. This disruption can create false information on the disc that neither a visual examination nor a computer examination can detect. When this occurs the disc should either be discarded or the information on it corrected.
Disruption on a disc package will not occur if a shock or acceleration is less than a particular amount; this amount depending on how much safety margin is required and the type of shock or acceleration received.
In the past, elaborate acceleration detectors that graphically recorded acceleration were used to check for possible damage to delicate apparatus. These detectors electronically monitored the movements of a pendulum or other mass and that information was converted to a graph.
Another acceleration monitor is shown in U.S. Pat. No. 4,068,613. This device used a deformable reservoir in which an interfacial barrier is ruptured above a predetermined shock, or acceleration. In the commercial embodiment the device of U.S. Pat. No. 4,068,613 employed a droplet in an enclosed capillary tube. The droplet is held away from the tube ends by slugs of air or air plugs. If a great enough acceleration occurs then the droplet or a portion of the droplet penetrates the air plug to wet an end of the tube. The commercial devices of U.S. Pat. No. 4,068,613 required careful control of the diameters and the relative interfacial tensions. Also, the longitudinal capillaries had a slight directional sensitivity.